045 
fxus63 kmqt 072058 
afdmqt 


Area forecast discussion 
National Weather Service Marquette Michigan 
358 PM EST Wednesday Jan 7 2009 


Short term (tonight and thursday)... 


The surface low over far southeastern Ontario will continue to shift 
northwestward...moving east of Maine by 12z Thursday. This will 
also allow the surface trough currently residing just south of the 
County Warning Area to lose its influence on the area. High pressure from the 
central Canadian prairies and North Dakota will continue to slowly 
push our way...bringing with it a significantly cooler airmass. 
Current temperatures over southern Manitoba are in the single to 
teens below zero...with single digits above zero over much of 
Minnesota. 


The main dilemma this period will be with lake effect snow 
showers...and how much snow will be able to fall across north and 
northwest favored snow belts. 


At this time...the most favored areas look to be over Gogebic and 
Ontonagon counties through late Thursday morning...and then Alger 
County through the entire period. 


Snow amounts over the western third of the County Warning Area will be aided by 
colder air sliding in at 850mb. Much of the County Warning Area should reside 
between -10c and -11c through 06z Thursday. At that time...colder 
air will begin to swing south-southwest from western Ontario. This will result 
in 850mb readings dropping to -15c west by 12z Friday...and falling 
to -18c west half by 00z Friday. This should help boost snow 
ratios. However...a less favorable wind of a more westerly 
direction west Thursday afternoon will assist in kicking out the 
moisture. 


So...the best time for significant accumulations look to be 
overnight tonight...before the colder air arrives aloft...but a 
convergent wind field lines up for Gogebic and Ontonagon counties. 
Will increase expected snow amounts here...to 3 to an isolated 5 
inches of lake effect. Will not issue any low end advisories for 
this amount...but later shifts will need to watch this area...and 
the east near Lake Superior if any bands persist for several hours. 


Another side effect of the cooling 850mb temperatures will be 
falling temperatures across the west half of the County Warning Area...through about 
15z. After 15z temperatures should only rebound a couple of degrees. 


For the north to northwesterly favored snow belts of Alger 
County...a quick 2 to 4 inches will remain possible. 




&& 


Long term (thursday night through wednesday)... 


NAM showing more reinforcing cold air with an upper level trough 
dropping southward from Ontario Thursday night and then another trough 
affecting the area Friday night. NAM taking 850-500 mb q-vector 
convergence out of the County Warning Area Thursday night and then NAM takes next system 
for Friday night and Sat to the south of the County Warning Area with southern County Warning Area on 
the northern edge of the system. GFS shows about the same thing 
along with the European model (ecmwf) and will cut probability of precipitation a bit in the south. In 
fact...all 3 models keep quantitative precipitation forecast to the south of the area and go with a 
lake effect scenario and will go with this idea for now. Lake effect 
will continue and will go likely probability of precipitation in northerly lake effect snow 
belts. Looks like the event will be long and drawn out and thinking 
is up to 5 inches of snow is possible in a 12 hour period or so in a 
few spots but mostly 1-3 inches each 6-12 hour period or so. Pushed 
system precipitation further south and this was the major change for this 
forecast. Did not make many changes to going temperatures. 


In the extended...GFS...ECMWF and Canadian all show a 500 mb trough 
across the eastern U.S. 00z sun which affects the County Warning Area on sun with 
amplification of the trough on Monday and Tuesday into Wednesday. What this will 
mean is lake effect will continue through the extended along with 
increasingly colder air arriving. Trimmed a few degrees off of highs 
on Monday and lows on Monday night and went drastically colder for 
Tuesday and Wednesday. Will see the coldest air of the season so far Tuesday and 
Wednesday and highs might not even make it to zero on Wednesday at all. 
Went with coldest guidance which was adjmel for Tuesday night and Wednesday 
temperatures. 


&& 


Aviation (for the 18z taf issuance)... 


Widespread snow this morning is beginning to wane as the inverted 
trough slowly slides south. Now the main form of moisture will be 
lake effect snow showers...as winds become more northerly late this 
afternoon/evening...and northwesterly towards the end of the 
forecast period. Drier...more stable air will advect in on Thursday 
as the low over the lower Great Lakes races on to the East 
Coast...but with a favorable wind direction off Lake 
Superior...little to no improvement will be realized at cmx. 


&& 


Marine (for the 4 PM Lake Superior forecast issuance)... 


Low pressure over Lake Ontario and its associated trough of low 
pressure across Lake Superior this evening will shift east 
overnight. High pressure across Saskatchewan and North Dakota this 
evening will shift to the Tennessee River valley and build 
slightly...and allow a ridge of high pressure to briefly cross the 
upper Great Lakes area Thursday night. Low pressure over the Central 
Plains Friday morning is then expected to move to far lower Michigan 
Saturday morning...and the northeastern states by late Saturday. 
Winds may near 30kt during this time period...but with the low 
remaining to our south...gales are not anticipated. The exiting low 
will make way for significant high pressure over The Rockies to push 
a ridge of high pressure over Lake Superior Saturday into Saturday 
night. Low pressure across south central Canada Sunday should shift 
across the Great Lakes region Monday. 


&& 


MQT watches/warnings/advisories... 


Upper Michigan...none. 
Lake Superior...none. 
Lake Michigan...none. 


&& 


$$ 


Short term...kf 
long term...07 
aviation...kf 
marine...kf 

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